In the related art, heating a battery group is achieved by arranging a plurality of silicone heating wires between single batteries. A relay is connected between the silicon heating wires in series and used as a switch, and two ends of each silicon heating wire are connected to a positive terminal and a negative terminal of the battery respectively. As shown in FIG. 1, the battery heating system in the related art includes a battery group, a main circuit switch 2′, a main circuit relay 3′, a protect circuit 4′, a relay 5′ and a heating wire 6′.
When the vehicle needs to be started, the main circuit switch 2′ is turned on, the protect circuit 4′ starts to work, and an environment temperature is determined by a temperature measuring device of the protect circuit 4′. When the environment temperature is less than a predetermined temperature, the relay 5′ is switched on, and the battery group discharges via the silicon heating wire 6′ with a low current. At this time, the silicon heating wire 6′ is working to generate heat so as to heat the battery group. When the temperature of the battery group reaches the predetermined temperature, the relay 5′ is switched off, the main circuit relay 3′ is switched on, and a vehicle control dial shows that the vehicle can be started. During running process of the vehicle, the battery group discharges and generates heat at the same time, and thus the environment temperature may be maintained at a required temperature, which solves the problem that a discharging efficiency of the battery group is low when the battery group is used in a relatively low environment temperature. When the battery group needs to be charged, the main circuit switch 2′ is turned on, and the protect circuit 4′ starts to work. When the environment temperature is less than the predetermined temperature, the relay 5′ is switched on, and the battery group discharges via the silicon heating wire 6′ with a low current, thus increasing the environment temperature. When the environment temperature reaches the predetermined requirement, the relay 5′ is switched off, the main circuit relay 3′ is switched on, and the battery group is charged. During the charging process, the battery group 1′ also generates heat, and thus the environment temperature may be maintained at a required temperature. Thus, a potential safety risk due to low environment temperature when the battery group is charged may be avoided.
However, there are at least following disadvantages in the related art: first, since the battery group discharges to the silicon heating wire with a low current, a heating power is relatively low; secondly, since the silicon heating wire heats a surrounding environment of the battery group so as to heat the battery group, the heat is generated outside of the battery group, and then gradually transmitted into the battery group. In conclusion, the battery group is heated under a very low heating speed, which usually needs several hours to heat the battery group, and thus it cannot meet requirements of users, especially those who want to use the vehicle or charge the vehicle immediately.
In addition, Chinese patent application No. 201010271405.0 discloses a battery heating method, in which a voltage or current is applied to the battery, and when the voltage of the battery is lower than a lower limit, the positive terminal and negative terminal of the battery are connected with each other via a load resistor, and the battery is heated through a discharge current. However, this method is achieved with the help of a charger, that is, the heating device disclosed in Chinese patent application No. 201010271405.0 is used as a part of the charger, the heating device is externally disposed, and the battery is heated before it is charged. Therefore, the battery could not be heated anytime and anywhere. That is, the battery must be connected to the charger, for example, a charging post, if the battery needs to be heated. Furthermore, the load resistor only can be connected with the battery via a charging port, which limits the heating current, and thus the battery cannot be heated quickly.